The uppermost layer of the skin, called epidermis, is always in a state of self-regeneration. At the bottom layer, keratinocyte stem cells divide into daughter cells, which are displaced outward, and which differentiate through successive overlying layers to enter the stratum corneum. Then, the keratinocytes die (apoptosis) and their cellular organella and cytoplasm disappear during the final process of differentiation. Intercellular lipids are primarily generated from exocytosis of lipid-containing granules called lamellar bodies, during the terminal differentiation. There must be a balance between the dying and newly formed keratinocytes, so the skin will constantly be in optimal state of health. Pugliese (2005) Advanced Professional Skin Care. 3-10.
Ionic signals play important role in the homeostatic mechanism of the epidermal barrier function. In normal skin, calcium is localized with high concentration in the epidermal granular layer, i.e., the uppermost layer of the epidermis, just below the stratum corneum. In keratinocytes, the extracellular level is maintained in a specific equilibrium with the intracellular concentrations. Tanojo et al. (2009) In: Handbook of Cosmetic Science and Technology (eds. A. O. Barel, M. Paye, H. I. Maibach), pp 173-182.
The skin serves numerous functions but its primary function is as a protective layer or barrier. The most important role of the skin for terrestrial animals is to protect the water-rich internal organs from the dry environment. This cutaneous barrier function of the skin resides in the upper most thin layer (approximately 10-20 μm in humans) called stratum corneum. The water impermeability of this layer is 1000 times-high than that of other membranes of living organisms. Wester & Maibach (1995) In: Percutaneous Penetration Enhancers. pp. 21-28.
In summary, combination of ions and some natural materials play an important role in the homeostasis of skin cells and the proper regeneration. A change in the barrier will change the calcium ion gradient in skin and lead to barrier repair process. A severe change might lead to a high degree of calcium signaling, which may induce the activation of various processes, from increased synthesis of skin components or messengers to the inflammatory reactions. Thus, there exists a need for compositions and methods for activating the barrier repair process to restore normal barrier function to skin adversely affected by environmental elements or pathological conditions.